The invention is in the field of fan manufacture and is particularly directed to fans composed of basic components capable of being easily altered in at least one dimension, preferably prior to assembly, so as to provide fans of different dimensions from like basic components.
Previously, the manufacture of fans differing in the dimensions of blade radial length and hub and blade axial length required keeping an inventory of different sized blades and hubs. Thus, the space requirements and cost of maintaining such an inventory for meeting the varied requirements of customers involve substantial costs of doing business.
Other substantial costs of doing business stem from the time and labor involved in positioning the blades relative to the hub and welding them thereto, such as when dealing with typically designed aluminum impellers commonly referred to as "blast fans", not to mention the materials and time involved in providing and changing work holding jigs.
It is therefore an object of the present invention to provide fans which are selectable in dimensions and are constructed from the same basic hub stock and blade stock.
Further, it is an object of the invention to provide the method and apparatus for manufacturing fans of variable dimension whereby the parts inventory therefore is substantially reduced, resulting in a corresponding reduction in space requirements and inventory costs.
It is an additional object of the invention to provide a basic piece of hub stock and a basic piece of blade stock from which fans of selected dimensions may be constructed.
It is an additional object of the invention to provide extruded lengths of hub and blade stock from which axial lengths of hub and blades may be trimmed or severed, according to the axial length requirements of each fan, and thereafter easily assembled.
It is a further object of the invention to provide that an impeller, formed by assembly of the blades and a hub, may be variable in diameter by trimming a radial length of the blades, preferably prior to such assembly.
It is an additional object of the invention to provide for the impeller being mountable upon shafts of varying diameters according to the requirements of the customer.
In a preferred embodiment of the invention, extruded lengths of hub and blade stock are provided, with the stock being cut according to the specifications of the customer regarding the axial length of the hub and blades as well as the radial length of the blades. The cross-sections of the blade and hub stocks are such that the blade roots are slidably received in the hubs during assembly thereof so that subsequent staking, glueing, or ultrasonic welding may be used to permanently attach the blades to the hubs. Aluminum and plastic materials are particularly adaptable to this construction.